1. Field of the Invention
The present invention relates to systems and methods for correction visual aberrations, and, more particularly, to such systems and methods for defining a region to be restricted from ablation.
2. Description of Related Art
Laser-in-situ-keratomileusis (LASIK) is a common type of laser vision correction method. It has proven to be an extremely effective outpatient procedure for a wide range of vision correction prescriptions. The use of an excimer laser allows for a high degree of precision and predictability in shaping the cornea of the eye. Prior to the LASIK procedure, measurements of the eye are made to determine the amount of corneal material to be removed from various locations on the corneal surface so that the excimer laser can be calibrated and guided for providing the corrective procedure previously determined by the measurements. Prior to the procedure, a microkeratome is typically used to make a thin, shallow incision in the cornea from the side, top, or bottom to create a hinged flap. During surgery the hinged flap is opened, the flap is positioned on or outside the hinge, and the excimer laser is then used to ablate corneal tissue commensurate with the predetermined corrective procedure.
Ablation is typically carried out discretely at each (x,y) coordinate along the cornea by a laser beam delivery and eye tracking system such as described in U.S. Pat. Nos. 5,980,513; 5,849,006; and 5,632,742, and application Ser. No. 09/566,668, all of which are commonly owned with the present invention, and the disclosures of which are herein incorporated by reference.
Preferably the size of the flap is sufficient for performing the ablation substantially without risk of ablating the hinge or flap. In prior art methods the surgeon could elect to allow the flap/hinge to be ablated, which is not to be desired, or to attempt to cover the flap/hinge, such as with a surgical instrument or partial contact lens, which may result in unwanted ablated material being deposited into the corneal bed.
In addition, a surgeon may desire to protect a region of the cornea from ablation for other reasons, which will be detailed in the following. Further, it would be desirable to protect other areas of the eye from ablation exposure.
It is therefore an object of the present invention to provide a system and method for protecting a selected region of an eye from exposure to an ablating laser.
It is a further object to provide such a system and method for protecting a hinge and flap created by a microkeratome.
It is another object to provide such a system and method that are software-driven.
It is an additional object to provide such a system and method that function through a graphical user interface.
These and other objects are achieved by the present invention, one embodiment of which comprises a system for protecting a sector of tissue from exposure to surgically directed radiation. The system comprises a processor and input means, a camera, and an output screen in electronic communication with the processor.
A software package resident on the processor has means for receiving camera data containing an image of a region of tissue. The tissue region includes at least a portion of a predetermined area desired to receive therapeutic radiation. The software package also has means for routing the image for display on the screen and means for superimposing on the displayed image first indicia indicative of the predetermined area. Means are also included for receiving via the input means data on a location of a sector of the tissue desired to be protected from the radiation and for superimposing on the displayed image second indicia indicative of the sector.
In a specific embodiment of the system the tissue comprises an eye and the predetermined area comprises at least a portion of the cornea. This is not intended as a limitation, however, and alternate tissue sites, such as internal organs, skin could also be irradiated using the graphical user interface of the system.
The method of the present invention, which is for protecting a sector of tissue from exposure to surgically directed radiation, comprises the step of receiving an image of a region of tissue and displaying the image. First indicia are superimposed on the displayed image, the first indicia indicative of the predetermined area. Data are received on a location of a sector of the tissue desired to be protected from the radiation, and second indicia are superimposed on the displayed image, the second indicia indicative of the sector.
In a preferred embodiment the method is employed on an eye, as for the system discussed above.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.